1. Field of the Invention
The present invention relates to a magnetic recording medium having a magnetic layer containing mainly a magnetic or magnetizable powder and a binder.
2. Brief Description of the Prior Art
As a binder used for binding the magnetic or magnetizable powders to the supporting base for conventional magnetic recording medium such as magnetic tapes have been employed, for example, vinyl chloride-vinyl acetate-vinyl alcohol copolymers or such copolymers in which the hydroxyl groups are modified. Although these copolymers are cured irradiation so that complicated cross-linked structures are formed in the molecules or between the magnetic or magnetizable powders or particles and the binders, such copolymers are so inactive in the movement of the molecular chains at ambient temperatures that a sufficient or complete cure by the irradiation with radiations is effected.
Where low molecular weight oligoesters or oligourethanes are employed as binders and cured by the irradiating, the coatings before curing are so soft that adhesion to the base film is caused when they were wound onto a roll, whereby pinholes are caused on the coatings and sometimes a large amount of magnetic or magnetizable powders or particles coated on the base film are removed during the calender treatment.